Sunday, April 17, 2016

Fire ant flight

The past few months have been a little hectic.  I’ve been rushing to finish my degree (I’m set to defend in May!) and get all my dissertation research published.  In spare moments I’ve been applying to jobs and planning my upcoming wedding.  In all the hustle M2M has fallen by the wayside.  But the mad dash is paying off.

Our work from Florida in 2013 has just been published!  My physicist friend Aaron and I spent that summer wrangling fire ant queens and getting them to fly on camera, all in an attempt to better understand how they move across landscapes and found new colonies.  Three years later our results are finally out in the journal PLoS ONE.

Aaron and I focused on two species of fire ants—the tropical fire ant Solenopsis geminata and the red imported fire ant Solenopsis invicta.  The first is native to the southern US, whereas S. invicta was accidentally introduced here from South America in the 1930s.  The two species now co-occur across the Deep South, including northern Florida.

Both species are interesting in that they produce two different types of queens.  One kind flies from her birth nest to found a new colony in an empty patch of soil.  The second kind, however, is a parasite that takes over other fire ant colonies.  Ant queens are normally extremely fat and nutritious, because they store a lot of energy to help them lay eggs and start new colonies.  But parasitic queens take over the resources of existing colonies, so they don’t need to store much energy and are usually much lighter.

Queens of Solenopsis geminata (A, B) and S. invicta (C, D).  In both species some queens have large energy-packed abdomens that help them found new colonies from scratch (A, C), while other queens are parasites that have smaller abdomens and take over existing colonies (B, D).

That’s where Aaron and I came in.  We measured how being heavier or lighter might affect how well a queen can fly.  It turns out that parasitic queens have much more favorable flight morphology—their lighter bodies probably allow them to fly much longer and farther in search of suitable nests to take over.  We calculated that they may fly up to four times as long as queens that start their colonies from scratch, and have a possible colonization area over 30 times as large!

The lighter abdomens of parasitic queens mean they can probably fly farther in search of nest sites.  If both queen types were dispersing from a colony here in Norman, Oklahoma, the parasitic queens would have a potential colonization area (blue circle, ~3.4 kilometer radius) over 30 times as large as those of queens that found their own colonies (red circle, ~550 meter radius).

Before we conducted our experiment, fire ant queens were thought to be able to fly for only 45 minutes, or maybe an hour at the most.  But we watched some queens fly for nearly an hour and a half!  It turns out fire ants are much better flyers than previously believed.  This might help explain how fire ants have managed to spread so rapidly here in the US.

This project was a particularly troublesome one, involving three trips to Florida, lots of trial and error, and a long and arduous publishing process.  It feels great to finally bring it to completion…and to have it out of the way before I defend my dissertation in a few weeks.

I’ve got a few other projects coming to a closeI’ll be sure to post about them when they come out.

And I look forward to devoting more time to M2M after I defend.

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